Anderzander Posted October 27, 2013 Share Posted October 27, 2013 A query to stop me setting fire to anything I'm wiring in my work light and will be using this circuit : There are a couple of things that I don't know about that I'd like to do.... I want to fit a warning light - I've seen them running off the switched live to the actual work light - but I'd like to put one on the earthed side of the switch. What I'd further like to do is make dual use of the fog light warning light on the dash. In the same way that the brake warning light works for the brake fluid level and the hand brake... So can I just wire into that warning lights feed ? Do I need to put some sort of capacitor on both circuits to stop the live bleeding back from one to another ? Lastly - looking at the warning light circuit the led just puts a feed to earth - can I therefore simply run the earth from my switch straight into the LED ? Apologies for the ignorance Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted October 27, 2013 Share Posted October 27, 2013 What's an 'onion' got to do with wiring? Coat and hat taken already.... Quote Link to comment Share on other sites More sharing options...
ejparrott Posted October 27, 2013 Share Posted October 27, 2013 What's an 'onion' got to do with wiring? Coat and hat taken already.... Beat me to it...!! A light will work when there is a potential difference across its legs. The charge light for example has +ve one side and -ve the other side with the engine off, but with the engine on it gets +ve on both legs, and so goes out. You can put a warning light in any part of the circuit, and when you give it power to one leg, it will light. I've never understood the whole switched live/switched earth argument - there's a reason earth cables should be able to handle the same power as the lives.... Quote Link to comment Share on other sites More sharing options...
mmgemini Posted October 27, 2013 Share Posted October 27, 2013 Why not a simple on/ off switch if you are using LED ? I have three LED's on my Defender. One a work light The other two mounted on the left side of the vehicle on the gutter. Both sets just use a simple on/ off switch. Why make life difficult Quote Link to comment Share on other sites More sharing options...
Steve King Posted October 27, 2013 Share Posted October 27, 2013 Why not use an on/off switch with a warning light built in? I have a TD5 Defender and used a "spotlight 2" switch that matched the existing switches and filled up a vacant slot in the centre switch panel. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted October 27, 2013 Share Posted October 27, 2013 whats with the two switches that both have to be switched to get that circuit to light the lamp ? All you need is to add a warning light supplied by the lamp side of the relay , so it is live when the light is . Then you need one on off switch in place of the two onions !! Quote Link to comment Share on other sites More sharing options...
Anderzander Posted October 27, 2013 Author Share Posted October 27, 2013 What's an 'onion' got to do with wiring? Coat and hat taken already.... I must be tired, I was thinking 'onion ?! - what onion !?' .... I'll get my coat ..... Beat me to it...!! A light will work when there is a potential difference across its legs. The charge light for example has +ve one side and -ve the other side with the engine off, but with the engine on it gets +ve on both legs, and so goes out. You can put a warning light in any part of the circuit, and when you give it power to one leg, it will light. I've never understood the whole switched live/switched earth argument - there's a reason earth cables should be able to handle the same power as the lives.... That's helpful - thank you. Any info on feeding into the rear fog warning light ? Would I need a diode to stop current bleeding back into the other circuit ? Why not a simple on/ off switch if you are using LED ? I have three LED's on my Defender. One a work light The other two mounted on the left side of the vehicle on the gutter. Both sets just use a simple on/ off switch. Why make life difficult It's a fair point ! I think I only planned it that was so I could run thinner wire to the front switch. Why not use an on/off switch with a warning light built in? I have a TD5 Defender and used a "spotlight 2" switch that matched the existing switches and filled up a vacant slot in the centre switch panel. Mines a 2000 td5 so no centre console - I wanted a separate warning light and if I can on the dash. I also seemed to struggle to find an on / on switch with a warning light ? whats with the two switches that both have to be switched to get that circuit to light the lamp ? All you need is to add a warning light supplied by the lamp side of the relay , so it is live when the light is . Then you need one on off switch in place of the two onions !! It's a two way circuit - you only need to click one / either switch to turn the light on or off. Like a two way circuit in most house stairs. I want to be able to turn it on and off from either the drivers seat or the back door. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted October 27, 2013 Share Posted October 27, 2013 I only use speaker wire to the two on the side of my truck. Later when I get the electrics done on the trailer. I'll use speaker cable to the LED at the back. A run of over three metres. Quote Link to comment Share on other sites More sharing options...
Maverik Posted October 28, 2013 Share Posted October 28, 2013 Beat me to it...!! A light will work when there is a potential difference across its legs. The charge light for example has +ve one side and -ve the other side with the engine off, but with the engine on it gets +ve on both legs, and so goes out. You can put a warning light in any part of the circuit, and when you give it power to one leg, it will light. I've never understood the whole switched live/switched earth argument - there's a reason earth cables should be able to handle the same power as the lives.... Earth switching circuits (using relays) are generally inherently "safer" in the way that when the switch is not switched on, it allows you the position of permanently live terminals to be located further away from the operator, thus mitigating, chances of switch faults and electrocution type events. It took me a while to get my head around this too... Quote Link to comment Share on other sites More sharing options...
Maverik Posted October 28, 2013 Share Posted October 28, 2013 You should have a shot at this, might help your understanding of electricity... http://www.yenka.com/en/Free_home_licences/ Quote Link to comment Share on other sites More sharing options...
ejparrott Posted October 28, 2013 Share Posted October 28, 2013 I'm not familiar enough with the Defender's warning light system to know if you could utilise it. I suppose you could put a diode in each feed to it, that would stop any current feeding the other circuits when one was live. Couldn't tell you how to size a diode for it though, I only know what they do, not what power they handle! Quote Link to comment Share on other sites More sharing options...
Anderzander Posted October 28, 2013 Author Share Posted October 28, 2013 Thanks - I've been trying to trace the circuits for the brake light and it's dual feeds and that has a diode on each feed. I'll do some more digging and see if I can find out the specs for them. Using the existing warning light is perhaps a bit pedantic, but it's a learning exercise and will end up looking a little more factory fit. Quote Link to comment Share on other sites More sharing options...
Maverik Posted October 28, 2013 Share Posted October 28, 2013 I was just playing about, you will need to put in a few diodes as already said. something like a 3A 1000v one would probably do you. And depending on when you r tapped into the warning light you may have to pop in another resistor, but chances are you'll be ok, if you're just tapping into its 12v supply, as I believe the voltage reduction resistor is accommodated in the actual warning light module itself. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted October 28, 2013 Author Share Posted October 28, 2013 Wow - thanks Maverik. For ease of wiring it would be better to run the warning light from the switch side of the circuit, rather than the light side. Hopefully there is no issue with that as it would save another wire running the full length of the Landy. Should be OK, as that must be how an illuminated switch works? I just googled 'land rover defender diode' and bizarrely it found a post from Ralph: these are the correct diodes that sit within the main/dash area loom. according to my parts book, there should be 3 fitted http://www.brit-car.co.uk/product.php/81238/0/diode_pektron_def___disco1___rrc Quite expensive for what it is ? If I can confirm its the one behind the warning lights it might serve to provide a rating. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted October 28, 2013 Author Share Posted October 28, 2013 How strange - stick a 'j' on the end and it's sold by jaguar for 11pence ? http://www.brit-car.co.uk/product.php/251839/0/diode_pektro Quote Link to comment Share on other sites More sharing options...
Maverik Posted October 28, 2013 Share Posted October 28, 2013 Wow - thanks Maverik. For ease of wiring it would be better to run the warning light from the switch side of the circuit, rather than the light side. Hopefully there is no issue with that as it would save another wire running the full length of the Landy. Should be OK, as that must be how an illuminated switch works? I just googled 'land rover defender diode' and bizarrely it found a post from Ralph: Quite expensive for what it is ? If I can confirm its the one behind the warning lights it might serve to provide a rating. The problem with not putting the "tell" on the light side is that your dash warning light will still light up even if the bulb has broken, having it on the other side shows you that the light is bust if the "tell" doesn't come on... I guess as its a light you'll know its bust as it wont come on, but in other circumstances when the thing you are switching is less obvious, its handy to know that the "thing" is actually active and not broken hence where you take your "tell" voltage from... if that makes sense... Also worth noting, be careful where you get your supplies from when taking them from the main wiring loom, its easier than you think to overload certain supplies, and that's the last thing you want to do... I'd be wanting to put another inline fuse somewhere is you're not entirely sure where the original supply is fused... Quote Link to comment Share on other sites More sharing options...
Anderzander Posted October 28, 2013 Author Share Posted October 28, 2013 That's good info - thank you ! I'm learning loads The supply is ok - the purple permanently live feed into the back of the td5 is for a trailer supply and is unused and fused at 30amps under the seat. I'll put a 5 amp fuse on for the light and a 1 amp for the switch side. Incidentally google has told me the diode is rated at 1a and 100v. Quote Link to comment Share on other sites More sharing options...
Anderzander Posted November 8, 2013 Author Share Posted November 8, 2013 How strange - stick a 'j' on the end and it's sold by jaguar for 11pence ? http://www.brit-car.co.uk/product.php/251839/0/diode_pektro The diodes came in the post today : How is it that Land Rover want 71 times the price, for the same part, as Jaguar do ? What kind of mark up is that http://www.brit-car.co.uk/search.php?xSearch=aau5034 Quote Link to comment Share on other sites More sharing options...
Maverik Posted November 9, 2013 Share Posted November 9, 2013 You see it having a Green Oval logo on the packet makes it have 71 times more awesomeness... that all you're paying for... Quote Link to comment Share on other sites More sharing options...
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